A combined analysis ("meta-analysis") of eight case-control studies, demonstrated a statistically significant association between exposure to radon in the home and lung cancer risk. The estimated risk level was consistent with risks extrapolated from studies of underground miners, who are generally exposed to much higher radon levels. Related work confirmed an "inverse exposure-rate" effect for radon, i.e., for equal total exposure, exposures occurring at a lower rate for a longer time impart a greater risk than exposures occurring at a higher rate for a shorter time. This effect, however, diminished at low total exposure, such as found in houses. A study of lung cancer and indoor radon is underway in an area of China where many homes have high radon concentrations. A cohort study of 74,828 benzene exposed workers and 35,805 unexposed workers employed from 1972 through 1987 in 12 cities in China, concluded that benzene exposure was associated with a spectrum of hematologic neoplasms, including acute non-lymphocytic leukemia and non-Hodgkin's lymphoma. Risks for these conditions were elevated at average benzene-exposure levels of less than 10 ppm and tended to rise with increasing levels of exposure. A case-control study of 638 children under the age of 15 years with acute lymphoblastic leukemia (ALL) who were registered with the Children's Cancer Group and 620 matched controls, was carried out to evaluate the association of ALL and residential exposure to magnetic fields generated by nearby power lines. Results provided little evidence that living in homes characterized by high measured magnetic-field levels or by configurations of electrical power lines increases the risk of ALL in children. In addition, the study found no association between ALL and residential radon concentration. Exposure to chlorination products in water was associated with increased risk of rectal cancer, but not colon cancer, in one study and with increased risk of bladder cancer in a second study, but only among smokers.